It is common practice in the construction of buildings and the like to use a lifting mechanism, such as a crane, to lift structural beams, trusses, or other loads to a location that is often high above the ground. Often the load is attached to a lifting hook of the crane by one or more slings positioned to support the load while it is being lifted into place.
Once the load has been moved to the desired location, it is necessary to release it from the slings. Particularly where the load is being placed at an elevated location, it is highly desirable that an apparatus and method be provided for remotely releasing the load from the slings, so that, for example, a workman standing on the ground can release the load.
Safe practices and regulations typically make it inadvisable to have a workman located in the area where the load is to be placed, while the load is being lifted into place, particularly where the load is to be placed in an elevated location. As a result, if no apparatus or method is provided for remotely releasing the load, a workman may need to climb the structure to release the load after it has been set in place, and then descend to the ground before another load can be lifted into place. This results in considerable lost time and effort, particularly where a large number of heavy loads, such as beams and trusses, must be lifted into place and properly positioned at an elevated level.
It is also highly desirable that a remote release apparatus and method provide positive locking of the release apparatus whenever the slings are supporting the load, so that it cannot be inadvertently released while being lifted into place. It is further desirable, in some circumstances, that such a remote release apparatus and method include other components, such as spreader beams, slings, and control components, to form a lifting apparatus.
Prior approaches to providing such a remote release apparatus, and lifting apparatuses including such a remote release apparatus, have not been entirely satisfactory for meeting the needs outlined above. Such prior approaches are exemplified by: U.S. Pat. No. 3,895,836, to Barnes, entitled Structural Member Lifting And Releasing Device; U.S. Pat. No. 5,762,389, to Marler, entitled Apparatus For Latching And Unlatching A Load Suspended From A Lifting Crane; U.S. Pat. No. 5,791,710, to Marler, entitled Apparatus For Latching And Unlatching A Load Suspended From A Lifting Crane; and, U.S. Pat. No. 6,024,394, to Marler, entitled Apparatus With A Centering Member For Latching And Unlatching A Load Suspended From A Lifting Crane;
It is desirable, therefore, to provide an improved apparatus and method for lifting a load, and for remotely releasing the load once it has been set in place, in a manner that better fulfills one or more of the needs described above.